1. Field of the Invention
This invention relates to a control valve assembly for hydraulic brakes and more particularly to a control valve assembly having a pair of proportioning valve assemblies for a split brake system.
2. Description of the Prior Art
Conventionally, control valve assemblies for split brake systems have been proposed which include a pair of proportioning valve assemblies for each brake pressure supply line of the split brake system. The valve assemblies proportionally reduce increases in the output fluid pressures to increases in the magnitudes of the input fluid pressures in excess of a predetermined value. Each proportioning valve assembly includes a valve seat and a slidable piston on which a valve member is provided. Each proportioning valve assembly has a spring means which biases the piston into a desired position wherein the valve member is spaced from the valve seat when brake pressure is below a predetermined value, such as shown in the U.S. Pat. No. 3,669,505. This results in an increase in the number of parts and the complexity of construction. In addition, in order to modify the brake pressure in response to load conditions acting on the vehicle body, a further load-sensing spring means has to be provided. This requirement further increases complexity of construction.